Search Results (412)

African ground squirrels (Xerus spp.), the inhabitants of African arid zones, face extreme heat and water scarcity driving selection for metabolic optimization. We assembled and annotated the first mitogenomes of Xerus inauris and Xerus rutilus (16,525–16,517 bp), revealing conserved vertebrate architecture with genus-specific traits. Key features include Xerus rutilus’s elongated ATP6 (680 vs. 605 bp), truncated ATP8–ATP6 spacers (4 vs. 43 bp), and tRNA-Pro control regions with 78.1–78.3% AT content. Their nucleotide composition diverged from that of related sciurids, marked by reduced T (25.78–26.9%) and extreme GC skew (−0.361 to −0.376). Codon usage showed strong Arg-CGA bias (RSCU = 3.78–3.88) and species-specific elevations in Xerus rutilus’s UGC-Cys (RSCU = 1.83 vs. 1.17). Phylogenetics positioned Xerus as sister to Ratufa bicolor (Bayesian PP = 0.928; ML = 1.0), aligning with African biogeographic isolation. Critically, we identified significant signatures of positive selection in key mitochondrial genes linked to arid adaptation. Positive selection signals in ND4 (ω = 1.8 × background), ND1, and ATP6 (p < 0.0033) correspond to enhanced proton gradient efficiency and ATP synthesis–molecular adaptations likely crucial for optimizing energy metabolism under chronic water scarcity and thermoregulatory stress in desert environments. Distinct evolutionary rates were observed across mitochondrial genes and complexes: Genes encoding Complex I subunits (ND2, ND6) and Complex III (Cytb) exhibited accelerated evolution in arid-adapted lineages, while genes encoding Complex IV subunits (COXI) and Complex V (ATP8) remained highly conserved. These findings resolve the Xerus mitogenomic diversity, demonstrating adaptive plasticity balancing arid-energy optimization and historical diversification while filling critical genomic gaps for this xeric-adapted lineage. Full article

In the traditional classification system of the Lauraceae family based on morphology and anatomy, the phylogenetic position of the genus Sassafras has long been controversial. Chloroplast (cp) evolution of Sassafras has not yet been illuminated. In this study, we first sequenced and assembled the complete cp genomes of Sassafras, and conducted the comparative cp genomics, phylogenomics, and divergence time estimation of this ecological and economic important genus. The whole length of cp genomes of the 10 Sassafras ranged from 151,970 bp to 154,011 bp with typical quadripartite structure, conserved gene arrangements and contents. Variations in length of cp were observed in the inverted repeat regions (IRs) and a relatively high usage frequency of codons ending with T/A was detected. Four hypervariable intergenic regions (ccsA-ndhD, trnH-psbA, rps15-ycf1, and petA-psbJ) and 672 cp microsatellites were identified for Sassafras. Phylogenetic analysis based on 106 cp genomes from 30 genera within the Lauraceae family demonstrated that Sassafras constituted a monophyletic clade and grouped a sister branch with the Cinnamomum sect. Camphora within the tribe Cinnamomeae. Divergence time between S. albidum and its East Asian siblings was estimated at the Middle Miocene (16.98 Mya), S. tzumu diverged from S. randaiense at the Pleistocene epoch (3.63 Mya). Combined with fossil evidence, our results further revealed the crucial role of the Bering Land Bridge and glacial refugia in the speciation and differentiation of Sassafras. Overall, our study clarified the evolution pattern of Sassafras cp genomes and elucidated the phylogenetic position and divergence time framework of Sassafras. Full article

Background: Centromeric alpha satellite DNA is organized into higher-order repeats (HORs), whose precise structure is often difficult to resolve in standard genome assemblies. The recent telomere-to-telomere (T2T) assembly of the human genome enables complete analysis of centromeric regions, including the full structure of HOR arrays. Methods: We applied the novel high-precision GRMhor algorithm to the complete T2T-CHM13 assembly of human chromosome 21. GRMhor integrates global repeat map (GRM) and monomer distance (MD) diagrams to accurately identify, classify, and visualize HORs and their subfragments. Results: The analysis revealed a novel Cascading 11mer HOR array, in which each canonical HOR copy comprises 11 monomers belonging to 10 different monomer types. Subfragments with periodicities of 4, 7, 9, and 20 were identified within the array. A second, complex 23/25mer HOR array of mixed Willard’s/Cascading type was also detected. In contrast to the hg38 assembly, where a dominant 8mer and 33mer HOR were previously annotated, these structures were absent in the T2T-CHM13 assembly, highlighting the limitations of hg38. Notably, we discovered a novel 52mer HOR—the longest alpha satellite HOR unit reported in the human genome to date. Several subfragment repeats correspond to alphoid subfamilies previously identified using restriction enzyme digestion, but are here resolved with higher structural precision. Conclusions: Our findings demonstrate the power of GRMhor in resolving complex and previously undetected alpha satellite architectures, including the longest canonical HOR unit identified in the human genome. The precise delineation of superHORs, Cascading structures, and HOR subfragments provides unprecedented insight into the fine-scale organization of the centromeric region of chromosome 21. These results highlight both the inadequacy of earlier assemblies, such as hg38, and the critical importance of complete telomere-to-telomere assemblies for accurately characterizing centromeric DNA. Full article

This study presents an integrative investigation of four rare and threatened plant species—Taraxacum kok-saghyz L.E. Rodin, Astragalus rubtzovii Boriss., Schmalhausenia nidulans (Regel) Petr., and Rheum wittrockii Lundstr.—native to the Ile Alatau and Ketmen ridges of the Northern Tian Shan in Kazakhstan. Combining chloroplast genome sequencing, geobotanical surveys, and anatomical and population structure analyses, we aimed to assess the ecological adaptation, genetic distinctiveness, and conservation status of these species. Field surveys revealed that population structures varied across species, with T. kok-saghyz and S. nidulans dominated by mature vegetative and generative individuals, while A. rubtzovii and R. wittrockii exhibited stable age spectra marked by reproductive maturity and ongoing recruitment. Chloroplast genome assemblies revealed characteristic patterns of plastid evolution, including structural conservation in S. nidulans and R. wittrockii, and a reduced inverted repeat region in A. rubtzovii, consistent with its placement in the IR-lacking clade of Fabaceae. Morphological and anatomical traits reflected habitat-specific adaptations such as tomentose surfaces, thickened epidermis, and efficient vascular systems. Despite these adaptations, anthropogenic pressures including overgrazing and habitat degradation pose significant risks to population viability. Our findings underscore the need for targeted conservation measures, continuous monitoring, and habitat management to ensure the long-term survival of these ecologically and genetically valuable endemic species. Full article

Background: Chryseobacterium indologenes, an environmental bacterium, is increasingly recognized as an emerging nosocomial pathogen, particularly in Asia, and is often characterized by multidrug resistance. Objectives: This study aimed to investigate the genomic features of clinical C. indologenes isolates from Maharaj Nakorn Chiang Mai Hospital, Thailand, to understand their mechanisms of multidrug resistance, virulence factors, and mobile genetic elements (MGEs). Methods: Twelve C. indologenes isolates were identified, and their antibiotic susceptibility profiles were determined. Whole genome sequencing (WGS) was performed using a hybrid approach combining Illumina short-reads and Oxford Nanopore long-reads to generate complete bacterial genomes. The hybrid assembled genomes were subsequently analyzed to detect antimicrobial resistance (AMR) genes, virulence factors, and MGEs. Results: C. indologenes isolates were primarily recovered from urine samples of hospitalized elderly male patients with underlying conditions. These isolates generally exhibited extensive drug resistance, which was subsequently explored and correlated with genomic determinants. With one exception, CMCI13 showed a lower resistance profile (Multidrug resistance, MDR). Genomic analysis revealed isolates with genome sizes of 4.83–5.00 Mb and GC content of 37.15–37.35%. Genomic characterization identified conserved resistance genes (bla_IND-2, bla_CIA-4, adeF, vanT, and qacG) and various virulence factors. Phylogenetic and pangenome analysis showed 11 isolates clustering closely with Chinese strain 3125, while one isolate (CMCI13) formed a distinct branch. Importantly, each isolate, except CMCI13, harbored a large genomic island (approximately 94–100 kb) carrying significant resistance genes (bla_OXA-347, tetX, aadS, and ermF). The absence of this genomic island in CMCI13 correlated with its less resistant phenotype. No plasmids, integrons, or CRISPR-Cas systems were detected in any isolate. Conclusions: This study highlights the alarming emergence of multidrug-resistant C. indologenes in a hospital setting in Thailand. The genomic insights into specific resistance mechanisms, virulence factors, and potential horizontal gene transfer (HGT) events, particularly the association of a large genomic island with the XDR phenotype, underscore the critical need for continuous genomic surveillance to monitor transmission patterns and develop effective treatment strategies for this emerging pathogen. Full article

Tripterygium wilfordii has extremely important pharmaceutical value in both traditional and modern medicine. The mitogenome of T. wilfordii was subjected to assembly and annotation with Nanopore long reads and Illumina short reads in this study. The mitogenome is 720,306 bp in length and is responsible for encoding 55 specific genes, including 35 protein-coding genes (PCGs), 17 transfer RNA (tRNA) genes, and 3 ribosomal RNA (rRNA) genes. Upon repetitive sequence analysis, 223 simple sequence repeats (SSRs), 24 long tandem repeats (LTRs), and 47 dispersed repetitive sequences (DRSs) were identified. The 24 common PCGs were used for phylogenetic analysis, which revealed that T. wilfordii is more closely related to Euonymus alatus. Moreover, mitochondrial plastid DNA (MTPT) analysis revealed eight MTPTs in the mitochondrial genome. Furthermore, 600 RNA-editing sites were detected in the protein-coding genes according to RNA-seq results. Among these genes, the ccmB gene contained the greatest number of sites, followed by the nad4 gene. This is the first study to report the T. wilfordii mitogenome and illustrate its linear structure. The findings of this study will help elucidate the evolution of the T. wilfordii mitogenome and facilitate its potential application in genetic breeding. Full article

Plant mitochondrial genomes exhibit extensive size variability and structural complexity. Here, we report the complete mitochondrial genome of Trichopus zeylanicus, an endemic medicinal plant from the Western Ghats. The mitochondrial genome was assembled using a combination of Illumina short-read and PacBio long-read sequencing technologies, followed by extensive annotation and comparative analysis. The circular mitogenome spans 709,127 bp with a GC content of 46%, encoding 32 protein-coding genes, 17 tRNAs, and three rRNAs. Comparative analysis with other monocot mitochondrial genomes revealed conserved gene clusters but also significant lineage-specific rearrangements. Despite genome size similarities, T. zeylanicus displayed marked divergence in gene order, suggesting that genome size does not necessarily correlate with structural conservation. The genome contains 6.7% chloroplast-derived sequences and 324 predicted RNA-editing sites, predominantly in the first and second codon positions. Phylogenetic analysis based on mitochondrial genes placed T. zeylanicus as a distinct lineage within Dioscoreales, supporting its evolutionary uniqueness. This work provides the first mitogenomic resource for Dioscoreales and advances our understanding of mitochondrial diversity and evolution in monocots. Full article

Paeonia ludlowii, a critically endangered species endemic to Tibet, China, possesses significant ornamental, culinary, and medicinal value. However, its mitochondrial genome remains understudied, limiting insights into its evolutionary mechanisms and constraining conservation genetics applications and molecular breeding programs. We present the first complete assembly and comprehensive analysis of the P. ludlowii mitochondrial genome. Most remarkably, we discovered that the P. ludlowii mitogenome exhibits an atypical dual-circular structure, representing the first documented occurrence of this architectural feature within the genus Paeonia. The assembled genome spans 314,371 bp and encodes 42 tRNA genes, 3 rRNA genes, and 31 protein-coding genes, with a pronounced adenine–thymine bias. This multipartite genome structure is characterized by abundant repetitive elements (112 functionally annotated SSRs, 33 tandem repeats, and 945 dispersed repeats), which potentially drive genome rearrangements and facilitate adaptive evolution. Analyses of codon usage bias and nucleotide diversity revealed highly conserved gene expression regulation with limited variability. Phylogenetic reconstruction confirms that P. ludlowii, P. suffruticosa, and P. lactiflora form a monophyletic clade, reflecting close evolutionary relationships, while extensive syntenic collinearity with other Paeonia species underscores mitochondrial genome conservation at the genus level. Extensive inter-organellar gene transfer events, particularly from chloroplast to mitochondrion, suggest that such DNA exchanges enhance genetic diversity and promote environmental adaptation. The discovery of the dual-circular architecture provides novel insights into plant mitochondrial genome evolution and structural plasticity. This study elucidates the unique structural characteristics of the P. ludlowii mitochondrial genome and establishes a crucial genetic foundation for developing targeted conservation strategies and facilitating molecular-assisted breeding programs for this endangered species. Full article

Hippophae rhamnoides subsp. sinensis is extensively found in China, where the annual precipitation ranges from 400 to 800 mm. It is the most dominant species in natural sea buckthorn forests and the primary cultivar for artificial ecological plantations. Additionally, it exhibits significant nutritional and medicinal value, making it a renowned eco-economic tree species. Despite extensive research into its ecological functions and health benefits, the mitochondrial genome of this widespread species has not yet been published, and knowledge of the mitochondrial genome is crucial for understanding plant environmental adaptation, evolution, and maternal inheritance. Therefore, the complete mitochondrial genome was successfully assembled by aligning third-generation sequencing data to the reference genome sequence using the Illumina NovaSeq 6000 platform and Nanopore Prometh ION technologies. Additionally, the gene structure, composition, repeat sequences, codon usage bias, homologous fragments, and phylogeny-related indicators were also analyzed. The results showed that the length of the mitochondrial genome is 454,489 bp, containing 30 tRNA genes, three rRNA genes, 40 PCGs, and two pseudogenes. A total of 411 C-to-U RNA editing sites were identified in 33 protein-coding genes (PCGs), with higher frequencies observed in ccmFn, ccmB, nad5, ccmC, nad2, and nad7 genes. Moreover, 31 chloroplast-derived fragments were detected, accounting for 11.86% of the mitochondrial genome length. The ccmB, nad4L, and nad7 genes related to energy metabolism exhibited positive selection pressure. The mitochondrial genome sequence similarity between H. rhamnoides subsp. sinensis and H. tibetana or H. salicifolia was 99.34% and 99.40%, respectively. Fifteen shared gene clusters were identified between H. rhamnoides subsp. sinensis and H. tibetana. Phylogenetically, the Rosales order showed close relationships with Fagales, Fabales, Malpighiales, and Celastrales. These findings provide fundamental data for exploring the widespread distribution of H. rhamnoides subsp. sinensis and offer theoretical support for understanding the evolutionary mechanisms within the Hippophae genus and the selection of molecular breeding targets. Full article

Parasitic diseases can be a significant constraint on aquaculture industries, which continue to develop in response to the rise in global demand for sustainable protein sources. Blood flukes, Cardicola forsteri and Cardicola orientalis, are economically significant parasites of Southern bluefin tuna (Australia), Pacific bluefin tuna (Japan), and Atlantic bluefin tuna (Mediterranean) as they are responsible for blood vessel obstruction in the gills leading to branchitis and mortalities when untreated. Here, we have defined the mitochondrial genomes for these species—the first for any aporocotylids. Oxford nanopore long-read sequencing was used to sequence C. orientalis from a single individual. The mitochondrial genome of C. forsteri was assembled and curated from available sequence data. Both Cardicola spp. mitogenomes contained 12 protein coding, 2 ribosomal and 22 tRNA genes, with the gene order matching that of Asian schistosomes. A control region was identified for each species which contained long and short repeats; the region for C. forsteri was longest, and the overall pattern differed between the two species. A surprisingly high nucleotide diversity was observed between the two species, generating interest into the mitochondrial genes of related species. This paper provides a useful resource for future genetics-based research of aporocotylids and other flatworm parasites of socioeconomic significance. Full article

Rhododendron purdomii Rehder & E. H. Wilson (Ericaceae) is a threatened ornamental and medicinal shrub or small tree species primarily distributed in the Qinling-Daba Mountains of Central China. To facilitate its conservation and utilization, the complete chloroplast genome of Rh. purdomii was sequenced, assembled, and characterized. The cp genome exhibited a typical quadripartite structure with a total length of 208,062 bp, comprising a large single copy (LSC) region of 110,618 bp, a small single copy (SSC) region of 2606 bp, and two inverted repeat (IR) regions of 47,419 bp each. The overall GC content was 35.81%. The genome contained 146 genes, including 96 protein-coding genes, 42 transfer RNA genes, and 8 ribosomal RNA genes. Structure analysis identified 67,354 codons, 96 long repetitive sequences, and 171 simple sequence repeats. Comparative genomic analysis across Rhododendron species revealed hypervariable coding regions (accD, rps9) and non-coding regions (trnK-UUU-ycf3, trnI-CAU-rpoB, trnT-GGU-accD, rpoA-psbL, rpl20-trnC-GCA, trnI-CAU-rrn16, and trnI-CAU-rps16), which may serve as potential molecular markers for genetic identification. Phylogenetic reconstruction confirmed the monophyly of Rhododendron species and highlighted a close relationship between Rh. purdomii and Rh. henanense subsp. lingbaoense. These results provide essential genomic resources for advancing taxonomic, evolutionary, conservation, and breeding studies of Rh. purdomii and other species within the genus Rhododendron. Full article

Platycrater arguta (Hydrangeaceae), a rare and endangered Tertiary relict shrub endemic to East Asia, holds significant ecological and evolutionary value. However, the P. arguta mitochondrial (mt) genome remains unexplored, limiting insights into its cytoplasmic evolution and phylogenetic relationships. In this study, a complete mt genome of P. arguta was sequenced, and we assembled the mt genome into two linear contigs for description, due to the complexity of its chromosome structure. The mt genome encodes 37 protein-coding genes, 27 tRNA genes, and three rRNA genes. A total of 687 RNA editing sites were predicted, and the most RNA editing sites were found in the nad4 gene. Repeat sequences with different sizes were detected in the mt genome, including 160 simple sequence repeats, 26 tandem repeats, and 320 dispersed repeats. Phylogenetic analysis grouped P. arguta with Hydrangea macrophylla (Hydrangeaceae), which is closely related to Eucommiaceae and Ericaceae. This study provides the first assembled and annotated mt genome of P. arguta, which enhances our understanding of the genome of this relict plant in Hydrangeaceae. Taken together, this study offered foundational data for conservation strategies, molecular breeding, and evolutionary studies of this endangered relict species. Full article

Background: Saxifraga umbellulata var. pectinata (Saxifragaceae) is recognized as a genuine medicinal material from the Qinghai–Tibet Plateau in China. This paper presents the chloroplast (cp) genome of S. umbellulata var. pectinata, marking the first report for this genus. The Tibetan medicinal plants documented in ‘Chinese Medicinal Plant Resources’ are associated with their chloroplast genomes and medicinal mechanisms. Objective: In order to resolve any potential ambiguity in conventional classifications, this study reconstructs the evolutionary position of S. umbellulata var. pectinata within the genus by comparing its chloroplast genetic information with that of other groupings. Methods: The chloroplast genome of S. umbellulata var. pectinata was sequenced using the Illumina NovaSeq 6000 platform. Subsequent sequence assembly, annotation, and characterization were performed using bioinformatics analysis. The NJ phylogenetic tree was constructed using MEGA 7.0 software. Results: The complete chloroplast genome of S. umbellulata var. pectinata is 146,549 bp in length, comprising four subregions: a large single-copy (LSC) region of 79,318 bp and a small single-copy (SSC) region of 16,390 bp, separated by a pair of inverted repeat (IR) regions each 25,421 bp long. This cp genome contains 131 genes, including 86 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The overall GC content is 38.1%. Phylogenetic analysis based on 20 cp genomes indicates that S. umbellulata var. pectinata is closely related to Saxifraga sinomontana and Saxifraga stolonifera. Full article

The Fabaceae family, the third-largest among flowering plants, is nutritionally vital, providing rich sources of protein, dietary fiber, vitamins, and minerals. Leguminous plants, such as soybeans, peas, and chickpeas, typically contain two to three times more protein than cereals like wheat and rice, with low fat content (primarily unsaturated fats) and no cholesterol, making them essential for cardiovascular health and blood sugar management. Since the release of the soybean genome in 2010, genomic research in Fabaceae has advanced dramatically. High-quality reference genomes have been assembled for key species, including soybeans (Glycine max), common beans (Phaseolus vulgaris), chickpeas (Cicer arietinum), and model legumes like Medicago truncatula and Lotus japonicus, leveraging long-read sequencing, single-cell technologies, and improved assembly algorithms. These advancements have enabled telomere-to-telomere (T2T) assemblies, pan-genome constructions, and the identification of structural variants (SVs) and presence/absence variations (PAVs), enriching our understanding of genetic diversity and domestication history. Functional genomic tools, such as CRISPR-Cas9 gene editing, mutagenesis, and high-throughput omics (transcriptomics, metabolomics), have elucidated regulatory networks controlling critical traits like photoperiod sensitivity (e.g., E1 and Tof16 genes in soybeans), seed development (GmSWEET39 for oil/protein transport), nitrogen fixation efficiency, and stress resilience (e.g., Rpp3 for rust resistance). Genome-wide association studies (GWAS) and comparative genomics have further linked genetic variants to agronomic traits, such as pod size in peanuts (PSW1) and flowering time in common beans (COL2). This review synthesizes recent breakthroughs in legume genomics, highlighting the integration of multi-omic approaches to accelerate gene cloning and functional confirmation of the genes cloned. Full article

Complete chloroplast genome sequences are widely used in the analyses of phylogenetic relationships among angiosperms. As a species-rich genus, species diversity centers of Saxifraga L. include mountainous regions of Eurasia, such as the Alps and the Qinghai–Tibetan Plateau (QTP) sensu lato. However, to date, datasets of chloroplast genomes of Saxifraga have been concentrated on the QTP species; those from European Alps are largely unavailable, which hinders comprehensively comparative and evolutionary analyses of chloroplast genomes in this genus. Here, complete chloroplast genomes of 19 Saxifraga species were de novo sequenced, assembled and annotated, and of these 15 species from Alps were reported for the first time. Subsequent comparative analysis and phylogenetic reconstruction were also conducted. Chloroplast genome length of the 19 Saxifraga species range from 149,217 bp to 152,282 bp with a typical quadripartite structure. All individual chloroplast genome included in this study contains 113 unique genes, including 79 protein-coding genes, four rRNAs and 30 tRNAs. The IR boundaries keep relatively conserved with minor expansion in S. consanguinea. mVISTA analysis and identification of polymorphic loci for molecular markers shows that six intergenic regions (ndhC-trnV, psbE-petL, rpl32-trnL, rps16-trnQ, trnF-ndhJ, trnS-trnG) can be selected as the potential DNA barcodes. A total of 1204 SSRs, 433 tandem repeats and 534 Large sequence repeats were identified in the 19 Saxifraga chloroplast genomes. The codon usage analysis revealed that Saxifraga chloroplast genome codon prefers to end in A/T. Phylogenetic reconstruction of 33 species (31 Saxifraga species included) based on 75 common protein coding genes received high bootstrap support values for nearly all identified nodes, and revealed a tree topology similar to previous studies. Full article